The present invention relates to a apparatus for the damping of oscillations in elevator cars and, in particular, to an apparatus for attenuating horizontal shocks in elevator cars.
High speed elevators place high demands on the precision of the guide rail alignment for the elevator cars. An inaccuracy in the alignment, as well as bad rail joints, can cause intermittent and jerky lateral movement of the car body and, in this manner, reduce the ride comfort with respect to vibration and noise. Such lateral movement becomes increasingly noticeable at higher speeds since it is related to the square of the car velocity. It is generally known to provide vibration damping elements of a variety of types and at different points between the body of the car and the car suspension. This type of vibration damping requires a compromise between soft and hard damping, wherein the hard damping reduces the ride comfort and the soft damping can cause high lateral deviation, both with corresponding unpleasant ride consequences.
U.S. Pat. No. 4,660,682 shows an elevator system in which the lower portion of an elevator car is supported for horizontal movement in all directions on roller or sliding guides, and the upper portion is held in an intermediate position by means of damping elements between the car sling and the car The horizontal deviation of the lower portion of the car takes place against the spring tensions centering the car. In addition to the spring tensioning, a mechanical limit centering device is provided which consists of an operating cylinder and linkage.
The action of the mechanical centering device shown in U.S. Pat. No. 4,660,682 can transmit noise and shocks to the car. The deviation of the lower portion of the car corresponds to the movement of a pendulum, so that every point on the lower end of the car moves on a circular path around the center of rotation of the upper end of the car. In turn, this motion has the consequence that, in particular, the peripheral points on the lower end of the car must make a corresponding vertical movement. In view of the rigid support in the vertical direction for sliding and rolling, undesirable effects result, such as for instance one sided lifting or canting of the elevator car. In addition, it is difficult to integrate a load measurement device in this type of car support.
U.S. Pat. No. 4,113,064 describes a similar car mounting device. The mechanical limiting of lateral movement is performed with an electromagnet which is attached to the car support and, on excitation, attracts a rubber supported plate mounted on the body of the car. The resultant frictional connection prevents a further horizontal deviation of the car. However, the required vertical movement compliance is only partially available. This mechanical limiting device makes a noticeable knocking noise and it is not contemplated that the device be actuated during the travel of the car.